Hubless caster

ABSTRACT

A hubless caster assembly includes a caster body and at least one wheel, the wheel comprising a toroidal member having a bearing race, and a complementary bearing race supported by the caster body. Bearing elements in the races support the wheel in free rotation. The caster body may comprise a ring body having an axial opening, whereby the caster assembly has a large central aperture extending entirely therethrough. A centering ring may be secured in the axial opening with the complementary bearing race formed therein. A hub cap with visual treatment may be secured over the central aperture.

REFERENCE TO RELATED APPLICATION

This application claims priority based on U.S. Provisional PatentApplication Ser. No. 60/295,592, filed Jun. 4, 2001.

BACKGROUND OF THE INVENTION

The present invention relates generally to a caster and morespecifically to a hubless caster for use in office furniture (chairs,tables, desks) as well as other devices or conveyances used primarilyfor transport of materials and pushed by hand (grocery carts, wagons).This new device is a caster that allows better inherent stability,easier rolling, and affords easy customization to enhance the overallaesthetic of the supported object (chair, table, cart, file cabinet, orother pieces of furniture). For the purpose of this patent, the attacheddevice will assumed to be an office chair.

DESCRIPTION OF THE PRIOR ART

It can be appreciated that casters have been in use for decades. Castersare located between the chair and the floor on which the chair isrolling, and are usually used in groups of 4 or 5 per end device.Typically, caster designs tend to fall into one of two groups: the‘single wheel’ and the ‘twin wheel’. The single wheel caster consists ofone wheel with an axle through the center which is attached to a supportbase. The support base is fixed to the chair (or other object) by use ofa vertical pin that allows the caster to pivot about a generallyvertical axis while also permitting rotation of the wheel about agenerally horizontal axis, thereby allowing the caster to move in anydirection.

The other main type of caster design is the ‘twin wheel’ caster, whichis identical to the first mentioned except two wheels are used insteadof one. The two wheels share a common axle, but are free to rotateseparately. The axle is affixed to the vertically extending base at alocation in the middle of the two wheels. In this way, each wheel isfree to rotate in opposite directions, facilitating a change indirection of the chair direction. Also, the wheels may turn in the samedirection for straight-line movement of the chair.

The main problem of the ‘single wheel’ caster is its inability to turneasily about the pin pivot. The wheel needs to rotate about the straightline formed by the wheel's contact with the horizontal floor.Effectively, a portion of the contacting wheel needs to drag on thefloor instead of freely rolling. Additionally, the central axle runningthrough the centerline of the wheel is supported at the outsides of thewheel. These outside locations are unprotected from any collisions withother chairs or walls, often leading to a bent axle, which seriouslyimpairs the usability of the caster. This design is still availablethough is less commonly used in modern office furniture.

The ‘twin wheel’ caster offered an improvement over the ‘single wheel’in two important regards. The ability of the wheels to rotate inopposite directions at the same time greatly enhanced the ability toturn about the vertical pivot, making a change in overall direction ofthe chair very smooth. Also, the support of the central axle to thechair in the middle of the two wheels afforded greater protection of thethin axles, greatly reducing the possibility of damage to the axle andsubsequent loss of performance. One problem germane to this caster typeis the method of attachment of the wheel to the axle. Unlike the singlewheel with its axle attachment on the two faces of the wheel, the doublewheel design attaches each wheel to its respective end of the axle, theaxle support to the base being disposed between the two wheels. Thisattachment configuration creates some inherent stability inefficiencies.By not allowing the axle to go through the wheel, the loading of thewheel on the axle is not symmetric. That is, the inside of the wheel isfully loading the axle while the outside is not loading the axle at all.Also, the limited space remaining in the device for the wheel thicknessresults in thin wheels, which directly result in narrow annular(limited) bearing surfaces of the wheel on the axle.

The overall attachment of the wheel to the axle is inherently notcompletely stable. With the simple method employing a pin (axle) in ahole (in the wheel), the resulting configuration is often fairly looseand sloppy. This can be easily verified by inspection of any casters ofthis type. Simply moving the wheels by hand shows the amount of ‘play’in the assembly and lack of inherent design stability. Note theseeffects multiply over time as the friction in the joints further movesthe features from the design ideals.

Both types of casters, additionally, suffer common drawbacks. In itsmost common embodiment, the wheels turn on the axle, relying on slidingfriction to afford rotation. This type of friction is not as smooth andefficient as other types of motion. Additionally, over time the frictionremoves material in the hole, creating a larger hole and subsequent‘wobble’ as the tight fit in the axle is lost.

Also, both casters rely on the wheels transferring load to axles locatedat the exact centerline of the wheel (s). This, at first glance, appearsto be the most rational design dating back to the originalwheel-about-axle. Certainly, this configuration is most stable forwheels turning very quickly, for example bikes or motorcars. But forwheels whose primary purpose is to carry load and turn at very slowrotational speeds (5 rpm and often, for long periods of time, zero), thecenter axle is not ideal. Under many loading instances, the wheelsimpart a moment about the wheel centerline perpendicular to thedirection of travel, such as in turning of the caster. This momentoccurs because the force on the wheel (at the floor contact) ismultiplied by the distance to the axle, the wheel radius. This momentadds more loading of the aforementioned wheel/axle joint, furtherdecreasing the inherent stability of the overall device.

Finally, there is a common failing in casters of either of the commondesigns. Needless to say, a caster is of no use by itself. The solepurpose of a caster is to provide greater functionality (ease ofmovement) to the overall object (office chair). As a piece of a greaterwhole, the caster should have the ability to enhance the overall designcharacteristics of the chair. This may be accomplished by replicatingdesign features from the rest of the chair, using consistent materials,or in other ways complimenting the overall intent of the chair design.With the ‘twin caster’ design, the prominent wheels with their solidcenter walls, located on the outside of the device dominate theappearance of the caster assembly. This leads to few opportunities tocustomize this type of caster for a specific chair design.

With few opportunities for differentiation in the wheel, this casterdesign leads to the device being featured on almost all furnitureproducts today without sharing any design traits (materials, color,design features) with the entire chair. Caster designs remainconsistently the same from chair to chair, manufacturer to manufacturer,year to year.

The relevant prior art includes U.S. Pat. No. 4,045,096, a rotor ismounted within a shroud, and various embodiments of roller bearings areshown for mounting the rotor to the shroud. In U.S. Pat. No. 4,465,321,a hubless wheel is mounted within a fender that describes less than afull circle. The wheel is collapsible, and is supported by thesurrounding fender. U.S. Pat. No. 5,248,019 shows motorcycle and bicycleconstructions that use hubless wheels. The wheel is apparently mountedto the fixed rim with one bearing. U.S. Pat. Nos. 5,419,619 and5,490,719 relate to a bicycle construction. Both are directed to theprecise angular spacing of the bearings mounted on the fixed hoop of ahubless wheel assembly, and appear to rely on four bearings unequallyspaced bearings. There is no teaching of a caster using hubless wheels,nor of a hubless wheel construction in which two hubless wheels aremounted on opposite sides of a common base ring.

SUMMARY OF THE INVENTION

The present invention generally comprises a hubless caster device foruse with furniture, equipment, carts, and other conveyances. This newdevice provides better stability, better rolling functionality, and manyflexible design implementations.

In these respects, the hubless caster substantially departs from theconventional concepts and designs of the prior art, and in so doingprovides an apparatus primarily developed for the purpose of a uniquecaster for use in office furniture or equipment.

The hubless caster shares some basic features with prior art casterdesigns: the central base component providing structure and a verticalpin, which attaches the central base component to the chair and allowsthe caster to pivot about the vertical pin. However, the presentinvention is unique in a very fundamental way, which provides greatadvantages over existing art. The device employs two wheels, eachlocated at opposite ends of the base. The wheels are not disc shaped asis most common. Rather, the wheels are annular (doughnut shaped) with nocentral disk wall or any other structure inside the opening that extendsthrough the annulus. Thus the largest, most visually dominant portion ofthe typical prior art designs is eliminated, The outside diameter of thewheel is circular and smooth, for efficient ground-engaging contact. Theinside diameter is provided with a toroidal groove that is adapted toreceive roller bearings, either cylindrical or ball type. The centralbase component includes a ring body, and two arrays of roller bearingsare disposed at opposed sides of the ring body, each array engaging thegroove of one of the wheels. The bearings support the wheels and permitrolling friction of the wheel about an axis defined by the centeringring portion of the base. The two wheels share a common ring body but donot share a common axle, bearings, nor support groove, so that eachwheel is free to rotate independently. By eliminating the common centeraxle, the need for the center section of the base is obviated. Thus thewheels and the center base are open through-and through, greatlyaltering the visual appearance (compared to prior art designs) bypermitting light to pass through the center of the caster assembly.

The use of rolling bearings allows better rolling as line friction hasbeen virtually eliminated. Of course, bearings are very commonly used inwheel applications, mostly as ball bearings. However, in this inventionthe bearing arrangement differs in that the balls ride in grooves thatare integral to the wheel and the base. Also, the bearings are notconcentrated close to the axis of symmetry, as in central axle designsin the prior art, but are spaced apart near the outside diameter of thewheel where the wheel makes contact. This location provides a far morestable wheeled device in that any side loads (moment) are nottransmitted via a lever arm (the radius of the wheel) further out to thecenter of rotation. The loads are transmitted to the bearings, whichoccupy a minimum space, thereby reducing the lever arm and providingless play in the system. Also, the grooves ‘capture’ the bearings verytightly (each ball surrounded by four planes). In this way, the balledjoint has very little play and greatly reduces any wobble that occurswhen a wheel is simply supported by an axle.

The elimination of the small diameter central axle enhances stability byvirtue of the geometry of the mechanics of the assembly. Stiffness of asection is enhanced by geometry in which features are far from thecenter of neutral axis. (I.e., a pipe is stiffer than a rod if both aremade of same material and employ same amounts of material.) With thewheels (via the bearings and centering ring) riding on the base directly(and not on an axle), the entire base becomes sole support for thewheels, with the enhanced effects of better stiffness and therefore amore stable overall device. Additionally, the base is far stronger thana simple axle and is more resilient to any impact on the device, henceit has better longevity.

The elimination of a central axle and the material that would normallysurround it in the base provides the hubless caster with a distinctadvantage over the existing art. This ‘hubless’ feature removes thevisual prominence of the wheel and allows the base (in its simplifiedform) to be more apparent. This leads to greater opportunities tocustomize the caster by incorporating design elements of the overalldesign of the end device, such as a chair or furniture item orskateboard. If left open, the hubless caster will allow a skateboard orchair itself to appear to be ‘floating’. If desired, the central hublessarea may be used to add features that are consistent and/or distinctivewith the entire chair such as holes, cutouts, different colors,imprinted logos, reflective surfaces, translucent materials, similarmaterials, fabrics, and so on. The ease of customization will allow aninfinite number of possible customizations to allow the hubless casterto be tailored for visual distinctiveness and design conformance withthe overall aesthetic. This feature makes it very distinctive over theubiquitous black twin wheeled caster.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of the hubless caster depicting overallpart geometry and hubless center portion along with the king pincomponent.

FIG. 2 is an exploded view of the hubless caster assembly showing theinternal mechanical components.

FIG. 3 is a detail depicting location of bearings and retainers inrelation to the wheel.

FIG. 4 is a cross section view of the hubless caster assembly, takenalong line 4—4 of FIG. 1, showing relevant part mating geometry.

FIG. 5 is an exploded view of a further embodiment of the hubless casterutilizing a thinner structural frame which allows the king pin device tobe customized.

FIG. 6 is an exploded view of a further embodiment of the caster usingrollers rotating about pins fixed to the base of the device.

FIG. 7 is a detail perspective view showing a further embodiment of thedevice in which the frame contains features to allow accessory devicessuch as brakes, fenders, and keep-out safety devices as well asdifferent structural attachment methods to be employed.

FIG. 8 is a perspective of a further embodiment of the hubless caster inwhich the open hubless portion of the device is provided with adecorative hub.

FIG. 9 is an exploded view showing the relationship of the decorativehub and hubless caster of FIG. 8.

FIG. 10 is an exploded view of a further embodiment of the device inwhich the two wheels are attached to each other in a hubless design.

FIG. 11 is an exploded view of a further embodiment of the device inwhich a structural tube is fixed to the base. The tube carries the load,allowing the frame to be made of lower strength material than previousembodiments (for example, plastic instead of a metal).

FIG. 12 is a perspective view of a further embodiment of the hublesscaster of the present invention.

FIG. 13 is a cross-sectional side elevation of the embodiment shown inFIG. 12.

FIG. 14 is a cross-sectional view taken along line 14—14 of FIG. 13.

FIG. 15 is a cross-sectional view taken along line 15—15 of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention generally comprises a hubless caster assembly foruse with furniture, equipment, carts, and other conveyances. This newdevice provides better stability, better rolling functionality, and manyflexible design implementations.

With regard to FIGS. 1-4, the hubless caster assembly includes a ringbody 1 having an open center portion 11. A kingpin 4 extends outwardlyfrom the ring body 1 and is supported by an integral boss 12. (In thedrawings, similar reference characters denote similar elementsthroughout the several views.) The kingpin may be received in agenerally vertically oriented receptacle for pivoting motion about thekingpin axis, as is known in the prior art. The assembly also includes acentering ring 8, which is provided with an annular body 13 and areduced diameter portion 9 extending coaxially from the body 13. Atoroidal wheel 5 includes an outer surface adapted to beground-engaging, and an inner annular surface 14. A bearing race groove16 is formed in the surface 14 at the inner end thereof. A plurality ofbearings 6 are disposed in the race groove 16, interspersed with bearingspacers 7 that maintain the spacing of the bearings 6. The bearings 6may be rollers, balls, or the like. The inner diameter of the racegroove 16 is sufficiently small to clear the outer surface of theportion 9 of centering ring 8, so that each wheel 5 is supported by thebearings 6 for rotation thereabout. Likewise, the inner diameter ofportion 14 of each wheel 5 is greater than the outer diameter of portion13 of the centering ring, so that the wheels are free to rotate abouttheir respective centering rings. The wheels thus rotate independently,and are capable of counter-rotating, as when the caster is pivoted aboutthe kingpin 4. The close spacing of the centering ring surfaces torespective confronting surfaces of the wheels serves to limit theintrusion of dirt into the bearing space.

With regard to FIGS. 5 and 6, an alternative embodiment of the hublesscaster includes the ring body 1 and the kingpin 4′ extending from a boss12′. In this embodiment, the king pin 4′ is reinforced by incorporationof an extension 21 of the structural frame from its interior ringportion 1, allowing the king pin to function as before but without theneed to be a rigid structural piece. In this embodiment, a plurality ofpins 22 extend outwardly from each side of the ring body 1, and aplurality of roller bearings 24 are each secured on the end of one ofthe pins 22 by retainer 23. The wheels 5 and centering rings 8 functionsubstantially as described previously. In this embodiment, no bearingspacers 7 are required. Also the pins and their roller bearings may bearrayed in unequally spaced fashion about the ring body; for example,more of the bearings may be disposed at the lower half of the ring bodyto absorb the primarily vertical load on the wheels.

With reference to FIG. 7, the ring body I may extend in a nominal plane,and a connector member 26 may extend from the ring body in the sameplane. The distal end of the connector member 26 terminates in a rightangle flange 27 having bolt holes for attachment to an object or pieceof furniture. The flange 27 and the lug 28 to allow accessory devicessuch as brakes, fenders, and keep-out safety devices as well asdifferent structural attachment methods to be employed.

Note that the wheels and retaining rings have open central portions thatcorrespond to the opening 11 in the ring body. Thus the caster assemblyhas no hub, no center, and thus is much less massive in appearance thanprior art casters that have solid disk wheels and central bodies. Lightpassing through the aligned openings causes the caster assemblies tobecome rather unnoticeable, so that the furniture item appears to‘float’ on the floor.

On the other hand, the hubless feature may be exploited in an oppositemanner. As shown in FIGS. 8 and 9, a hub cap 29 may be affixed to theopening of at least one centering ring 8 of a caster assembly of theinvention. The hub cap 29 may bear a manufacturer's logo, or decorativeimagery or indicia, or fabric covering to match the upholstery of achair, or wood grain to match a desk, or the like. If the hub cap 29 istransparent or translucent, transmitted light will illuminate a logo orindicia borne thereon. The hub cap 29 is not necessary as a structuralelement, and may be removable, or replaceable. Note that the diameter ofthe cap 29 is only slightly less than the diameter of the wheels 8, sothat the caps 29 dominate the visual appearance of the caster assembly.Thus there is ample opportunity to stylize the appearance of the casterassembly in connection with the appearance and design of the end useitem supported by the caster assembly.

With reference to FIG. 10, a further embodiment of the hubless casterincludes the ring body 1 and kingpin 4 extending therefrom. In thisembodiment the opening 11 of the ring body is configured as a bearingrace, and the roller bearings 6 and spacers 7 are arrayed about theinner surface of the opening 11. Each wheel 30 is an annular objecthaving an outer tread portion 31 and an inner neck 32 that extendsthrough the bearing assembly to join the neck 32 of the wheel 30 on theopposite side of the ring body 1. The necks 32 engage the bearings 6 torotate freely therein, and the wheels 30 are joined for rotation incommon. This embodiment eliminates the centering rings, and simplifiesmanufacturing and parts count. It may be advantageous in situationswhere a caster is fixed in direction, in which case the kingpin may bereplaced by a non-pivoting mounting, as shown for example in FIG. 7.

Another embodiment of the invention, shown in FIG. 11, includes the ringbody 1 and kingpin 4 extending therefrom. The central opening 11 of thering body 1 secures a tube 34 extending rigidly therethrough. A wheel 36and centering ring 37 are assembled to a respective end of tube 34, withbearings 6 and spacers 7 secured in a race groove (as in the previousembodiments) in the inner surface of the wheel 36. In thus embodimentthe wheels rotate independently. The tube 34 carries the load, allowingthe body 1 to be formed of lower strength material (for example, plasticinstead of a metal) than embodiments described above.

An additional embodiment of the invention, shown in FIGS. 12-15,includes a ring body 1 and kingpin 4 extending therefrom. The ring body1 is provided with a pair of bearing race grooves 41 extending annularlyand coaxially, and disposed on either side of the ring body. A pair oftoroidal wheels 42 are provided, each wheel including an annular racegroove 43 at an inner surface portion thereof, the outer surface beingadapted to ground-engaging contact. The wheels are assembled to theirrespective sides of the body 1, with the bearing races 41 and 43disposed in confronting registration to contain a plurality of balls 44arrayed therein. The wheels 42 rotate independently in low frictionrolling motion on the balls 44. Note that the centering ring of previousembodiments is eliminated. The bearing arrangment in this embodiment maycomrprise the bearings 6 and spacers 7 of previous embodiments.

In all the embodiments described above, the construction shown allowsthe bearings to rotate about a common centerline, even though there isno shaft or other central structure in the assembly. The load istransmitted from the wheels to the bearings and to the body 1. Thisdesign, by providing a large cross-section at the bearing assembly,provides a stiffer structure than a simple axle device. The body 1 isthe main structural member and should be constructed of metal and/orstrong plastic materials using mass-production (injection) manufacturingtechniques or metal stamping. The body, by virtue of not having an axlethrough the center, allows the center section to be used for differentdesign features more consistent with the overall furniture piece, suchas holes, different materials, matching materials or textiles from thechair, and/or other design features replicated from the end useassembly.

The wheels 5 may be made of plastic or metal or rubber or a combinationthereof. They may have patterns or textures or color treatments employedin the outside treads. In general, both the centering rings and thewheels incorporate raceways to share the bearings and transmit loadsbetween the wheels to the frame. The raceways are either four flatannular surfaces or toroidally curved surfaces that match the bearingprofile. In either configuration, the raceways provide a firm, close-fitwith the balls. The shared geometry of the raceway between the wheelsand the centering ring is required although the apportionment is notcritical. That is, the enclosing cross section must be provided aboutthe bearings but the enclosing features may be in the wheel, thecentering ring, and/or may be provided through the addition of spacers.

The caster device described in any embodiment herein is infinitelyscaleable. It may be used for very small items to be moved or verylarge. Its most useable application may be for furniture (seating,storage devices, and desks). The most distinctive and changeable portionof the caster is the unique unused ‘center section’. Without need for acentral axle, the center base area may be used for design elements(logos, design features, different colors, symbols) or other additionalapparatus (level-measuring devices, stationary brakes, odometers,illumination, etc).

The foregoing description of the preferred embodiment of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and many modifications and variations are possible inlight of the above teaching without deviating from the spirit and thescope of the invention. The embodiment described is selected to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and with various modifications as suited to theparticular purpose contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto.

1. A caster assembly, including: a caster body; a wheel including anouter toroidal member having a large opening extending centrally throughsaid outer toroidal member, said outer toroidal member including a firstbearing race extending annularly therein; said caster body including aring body having an axial opening extending therethrough; bearing meansjoined to said ring body to support said wheel, said bearing meansincluding a second bearing race disposed in confronting, complementaryrelationship to said first bearing race, and a plurality of bearingelements retained in said first and second bearing races to directlysupport said outer toroidal member in freely rotating fashion; saidlarge central opening and said axial opening being co-extensive anddevoid of any structural member extending therein.
 2. The casterassembly of claim 1, further including means for securing said casterassembly to an end use object.
 3. The caster assembly of claim 2,wherein said means for securing includes a kingpin extending from saidcaster body.
 4. The caster assembly of claim 2, wherein said means forsecuring includes a mounting bracket extending from said caster body. 5.The caster assembly of claim 1, wherein said bearing means includes acentering ring secured in said axial opening.
 6. The caster assembly ofclaim 5, wherein said wheel includes an inner annular surface, and saidfirst bearing race is formed in said inner annular surface.
 7. Thecaster assembly of claim 6, wherein said centering ring includes anouter annular surface, and said second bearing race is disposed in saidouter annular surface of said centering ring.
 8. The caster assembly ofclaim 7, wherein said centering ring is disposed concentrically withinsaid axial opening and within said central opening of said wheel.
 9. Thecaster assembly of claim 1, wherein said axial opening and said centralopening comprise an aperture defining a wide unobstructed sight lineextending through said caster assembly.
 10. The caster assembly of claim9, further including a hub cap secured in said aperture.
 11. The casterassembly of claim 10, further including surface treatment means on saidhub cap to complement visually an end use object to which said casterassembly is connected.
 12. The caster assembly of claim 1, wherein saidbearing elements include a plurality of balls.
 13. The caster assemblyof claim 12, wherein said bearing elements includes a plurality ofbearing spacers interspersed between said balls.
 14. The caster assemblyof claim 1, wherein said bearing elements includes a plurality ofrollers.
 15. The caster assembly of claim 14, wherein said bearing meansincludes a plurality of bearing pins arrayed about said second bearingrace, each of said bearing pins supporting one of said bearing rollersfor rotation about an axis substantially parallel to the axis of saidaxial opening.
 16. The caster assembly of claim 1, wherein said bearingmeans includes a tubular member secured in said axial opening, saidtubular member having at least one end extending outwardly from saidring body.
 17. The caster assembly of claim 16, wherein said secondbearing race is disposed in said one end of said tubular member.
 18. Thecaster assembly of claim 17, further including a retaining ring securedto said one end of said tubular member.
 19. The caster assembly of claim1, wherein said ring body includes an outer annular surface, and saidsecond bearing race is disposed in said outer annular surface of saidring body.
 20. A caster assembly, including: a caster body; a pair ofwheels, each including an outer toroidal member having a large openingextending centrally through said outer toroidal member, said outertoroidal members including a pair of first bearing races, each extendingannularly in one of said outer toroidal members; said caster bodyincluding a pair of ring bodies having axial openings co-extendingtherethrough; bearing means joined to said ring bodies to support saidwheels, said bearing means including a pair of second bearing races,each disposed in confronting, complementary relationship to one of saidfirst bearing races, and a plurality of bearing elements retained insaid first and second bearing races to directly support said outertoroidal members in freely rotating fashion; said large central openingsof said outer toroidal members and said axial openings of said ringbodies being co-extensive and devoid of any structural member extendingtherein.
 21. The caster assembly of claim 20, further including meansfor securing said caster assembly to an end use object.
 22. The casterassembly of claim 21, wherein said means for securing includes a kingpinextending from said caster body.
 23. The caster assembly of claim 21,wherein said means for securing includes a mounting bracket extendingfrom said caster body.
 24. The caster assembly of claim 20, wherein saidbearing means includes a pair of centering rings secured in said axialopening.
 25. The caster assembly of claim 24, wherein each of saidwheels includes an inner annular surface, and each of said first bearingraces is formed in one of said inner annular surfaces.
 26. The casterassembly of claim 25, wherein each of said centering rings includes anouter annular surface, and each of said second bearing races is disposedin said outer annular surface of one of said centering rings.
 27. Thecaster assembly of claim 26, wherein said centering rings are disposedconcentrically within said axial opening and within said centralopenings of said wheels.
 28. The caster assembly of claim 20, whereinsaid axial openings and said central openings comprise an aperturedefining a wide unobstructed sight line extending through said casterassembly.
 29. The caster assembly of claim 28, further including atleast one hub cap secured in said aperture.
 30. The caster assembly ofclaim 29, further including surface treatment means on said hub cap tovisually complement an end use object to which said caster assembly isconnected.
 31. The caster assembly of claim 20, wherein said bearingelements include a plurality of balls.
 32. The caster assembly of claim31, wherein said bearing elements includes a plurality of bearingspacers interspersed between said balls.
 33. The caster assembly ofclaim 20, wherein said bearing elements includes a plurality of rollers.34. The caster assembly of claim 33, wherein said bearing means includesa plurality of bearing pins arrayed about each of said second bearingraces, each of said bearing pins supporting one of said bearing rollersfor rotation about an axis substantially parallel to the axis of saidaxial opening.
 35. The caster assembly of claim 20, wherein said bearingmeans includes a tubular member secured in said axial opening, saidtubular member having opposed ends extending axially outwardly from saidring body.
 36. The caster assembly of claim 35, wherein each of saidsecond bearing races is disposed in one of said opposed ends of saidtubular member.
 37. The caster assembly of claim 36, further including aretaining ring secured to said one end of said tubular member.
 38. Thecaster assembly of claim 20, wherein said pair of wheels each rotateindependently with respect to the other.
 39. The caster assembly ofclaim 1, wherein said wheel includes a neck portion adapted to bereceived in said annular surface of said axial opening, said firstbearing race formed in an outer annular surface of said neck portion.40. The caster assembly of claim 39, wherein said wheel includes a neckportion adapted to be received in said inner annular surface of saidaxial opening, said first bearing race formed in an outer annularsurface of said neck portion.
 41. The caster assembly of claim 39,further including a pair of said wheels, each wheel including a neckportion adapted to be received in said inner annular surface of saidaxial opening, said first bearing race formed in an outer annularsurface of said neck portion of each of said wheels.
 42. The casterassembly of claim 41, wherein said neck portions of said pair of wheelsare joined for rotation in common within said second bearing race. 43.The caster assembly of claim 14, wherein said bearing elements include aplurality of spacers interposed between said rollers.
 44. The casterassembly of claim 33, wherein said bearing elements include a pluralityof spacers interposed between said rollers.